G. SERTULARIA. 81 



SERTULARIA. 



A PLANT-FORMED Polypidom, branching; stem 

 usually flexuous or in zigzag ; cells alternate. 



The form of the Polypidoms which I have united in 

 the family of theSertularias varies considerably : some 

 have their branches dispersed, and form almost pani- 

 culated stems ; there are some whose stem is upright 

 with flexuous branches ; a great number have their 

 branches straight upon a flexuous stem : finally, there 

 are some whose divisions are dichotomous and diver- 

 gent, and which break, when dry, on the slightest at- 

 tempt to bend them. 



The substance of the Sertularias is horny- mem- 

 branous ; with sometimes a slight cretaceous incrus- 

 tation on the lower part of the Polypidom. 



Their colour, in general agreeably shaded, does 

 not equal the Corallines in brilliancy of tints. This 

 colour varies from white to a fawn, from rose-colour 

 to a tarnished green. 



They greatly differ in size ; some scarcely reach- 

 ing a centimetre, while others raise their branches 

 many decimetres high. 



They are found in all seas, and in all latitudes. 



FIR. 



1. SERTULARIA ahietina. Cells oval, tubular, 

 with a border entire ; bulging towards the stem. 



European seas. 



PECTINATED. 



2. SERTULARIA pectinata. Base or root branch- 

 Cor, L 



